springboot配置多数据源（JdbcTemplate方式）

在实际开发中可能会遇到需要配置多个数据源的情况，比如：需要使用多个host、需要使用多种数据库（MySql、Oracle、SqlServer...）

如果使用springboot开发，可做如下配置：

Config：

import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.jdbc.DataSourceBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.jdbc.core.JdbcTemplate;

import javax.sql.DataSource;

@Configuration
public class DataSourceConfig {

    @Bean(name = "testDataSource")
    @Primary
    @Qualifier("testDataSource")
    @ConfigurationProperties(prefix="spring.datasource.hikari.mysql")
    public DataSource testDataSource() {
        return DataSourceBuilder.create().build();
    }

    @Bean(name = "formalDataSource")
    @Qualifier("formalDataSource")
    @ConfigurationProperties(prefix = "spring.datasource.formal.mysql")
    public DataSource formalDataSource() {
        return DataSourceBuilder.create().build();
    }

    @Bean(name="testJdbcTemplate")
    public JdbcTemplate testJdbcTemplate (
            @Qualifier("testDataSource")  DataSource testDataSource ) {
        return new JdbcTemplate(testDataSource);
    }

    @Bean(name = "formalJdbcTemplate")
    public JdbcTemplate formalJdbcTemplate(
            @Qualifier("formalDataSource") DataSource formalDataSource){
        return new JdbcTemplate(formalDataSource);
    }
}

配置文件 application.properties

spring.datasource.hikari.mysql.jdbc-url =jdbc:mysql://mysql2.cdqdops.org:3306/standard?useUnicode=true&characterEncoding=utf-8&useSSL=false&allowMultiQueries=true
spring.datasource.hikari.mysql.username = root
spring.datasource.hikari.mysql.password = 123456
spring.datasource.hikari.mysql.driver-class-Name = com.mysql.jdbc.Driver

spring.datasource.formal.mysql.jdbc-url =jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf-8&useSSL=false&allowMultiQueries=true
spring.datasource.formal.mysql.username = root
spring.datasource.formal.mysql.password = 1314
spring.datasource.formal.mysql.driver-class-Name = com.mysql.jdbc.Driver

注意事项

使用多个数据源时，需要添加@Primary注解

@Primary：自动装配时当出现多个Bean候选者时，被注解为@Primary的Bean将作为首选者

当然,primary意味着"主要的",类似与SQL语句中的"primary key",有且只能有一个

开发时,别人将注释掉的代码恢复,出现了多个"@Primary",就导致了如下错误:

[root@app4 logs]# tail stdout.log 
Caused by: org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type 'javax.sql.DataSource' available: more than one 'primary' bean found among candidates: [mysqlDataSource, formalDataSource, sqlServerDataSource]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.determinePrimaryCandidate(DefaultListableBeanFactory.java:1381)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.determineAutowireCandidate(DefaultListableBeanFactory.java:1341)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1110)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory$DependencyObjectProvider.getIfUnique(DefaultListableBeanFactory.java:1728)
    at org.springframework.boot.autoconfigure.jdbc.DataSourceInitializerInvoker.getDataSourceInitializer(DataSourceInitializerInvoker.java:100)
    at org.springframework.boot.autoconfigure.jdbc.DataSourceInitializerInvoker.afterPropertiesSet(DataSourceInitializerInvoker.java:62)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1758)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1695)
    ... 32 common frames omitted